Wat Chedi Luang (a.k.a. Jedi Luang) was built in 1391 during the reign of King Saen Muang Ma, 8th ruler of the Mengrai dynasty. He intended the structure to house the ashes of his father, Ku Na. Appropriately, the site was designated as a 'ku luang' instead of a chedi since it was not intended to house relics of the Buddha.
The massive reliquary was expanded over the centuries, until it reached its final form in 1475, when King Tilokaraj made it the home of the Emerald Buddha, the most important cultural treasure in Thailand. At one point the reliquary--which had come to be known as a chedi--was 144 feet wide and 282 feet tall. Unfortunately, the pagoda was heavily damaged in the 1545 earthquake during the reign of Queen Mahadevi. The Emerald Buddha remained here for about six years after the earthquake, whereupon it was brought to Luang Prabang (in today's Laos) by King Setthathirat, who ruled Chiang Mai for a short period in the years following the earthquake.
The viharn, or worship hall, is a much newer structure decorated with naga (water snake) and peacock motifs.
According to Roy Hudson, visitors entering this temple should take note of the massive tree to the left of the entrance. Legend says that if this tree should ever fall, a great catastrophe will occur. A small building near the tree enshrines the "Spirit of the City" (Sao Intakin) that was moved from its original site in 1775.